Scientists at the University of Cambridge tested 39 sweeteners against 25 species of gut bacteria and found that roughly three-quarters of the sweeteners altered the growth of at least one bacterial species. Some slowed or stopped the growth of microbes associated with a healthy digestive system, according to the study published in Molecular Systems Biology.
To better reflect real-world use, the researchers also combined sweeteners with common substances including caffeine, vanillin, and several drugs. More than 100 unexpected interactions were observed. One notable combination was isosteviol, a sweetener compound, with duloxetine, a widely prescribed antidepressant. This pairing strongly suppressed two important gut bacteria involved in digestive health and blood sugar regulation, and it disrupted the balance of a simulated gut microbiome in ways that could relate to inflammation and immune responses.
The researchers caution that these effects were observed in laboratory experiments, not in humans, so the real-world health consequences remain unclear. They also note that people rarely consume sweeteners alone, which is why studying combinations matters, but further studies are needed before drawing conclusions about diet or medication safety.